Process for producing cyclohexylbenzene

ABSTRACT

In a process for producing cyclohexylbenzene, benzene and hydrogen are fed to at least one reaction zone. The benzene and hydrogen are then contacted in the at least one reaction zone under hydroalkylation conditions with a catalyst system comprising a molecular sieve having an X-ray diffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and 3.42±0.07 Angstrom, and at least one hydrogenation metal to produce an effluent containing cyclohexylbenzene. The catalyst system has an acid-to-metal molar ratio of from about 75 to about 750.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage Application of InternationalApplication No. PCT/US2008/072843 filed Aug. 12, 2008, which claimspriority from EP 08001564.7 filed Jan. 21, 2008, which claims priorityfrom U.S. Ser. No. 60/974,312 filed Sep. 21, 2007, all of which areincorporated herein by reference.

FIELD

The present invention relates to a process for producingcyclohexylbenzene and optionally for converting the resultantcyclohexylbenzene into phenol and cyclohexanone.

BACKGROUND

Phenol is an important product in the chemical industry and is usefulin, for example, the production of phenolic resins, bisphenol A,ε-caprolactam, adipic acid, and plasticizers.

Currently, the most common route for the production of phenol is theHock process. This is a three-step process in which the first stepinvolves alkylation of benzene with propylene to produce cumene,followed by oxidation of the cumene to the corresponding hydroperoxideand then cleavage of the hydroperoxide to produce equimolar amounts ofphenol and acetone. However, the world demand for phenol is growing morerapidly than that for acetone. In addition, the cost of propylene islikely to increase, due to a developing shortage of propylene. Thus, aprocess that uses higher alkenes instead of propylene as feed andcoproduces higher ketones, rather than acetone, may be an attractivealternative route to the production of phenols.

For example, oxidation of cyclohexylbenzene (analogous to cumeneoxidation) could offer an alternative route for phenol productionwithout the problem of acetone co-production. This alternative routeco-produces cyclohexanone, which has a growing market and is used as anindustrial solvent, as an activator in oxidation reactions and in theproduction of adipic acid, cyclohexanone resins, cyclohexanone oxime,caprolactam and nylon 6. However, this alternative route requires thedevelopment of a commercially viable process for producing thecyclohexylbenzene precursor.

It has been known for many years that cyclohexylbenzene can be producedfrom benzene by the process of hydroalkylation or reductive alkylation.In this process, benzene is heated with hydrogen in the presence of acatalyst such that the benzene undergoes partial hydrogenation toproduce cyclohexene which then alkylates the benzene starting material.Thus U.S. Pat. Nos. 4,094,918 and 4,177,165 disclose hydroalkylation ofaromatic hydrocarbons over catalysts which comprise nickel- and rareearth-treated zeolites and a palladium promoter. Similarly, U.S. Pat.Nos. 4,122,125 and 4,206,082 disclose the use of ruthenium and nickelcompounds supported on rare earth-treated zeolites as aromatichydroalkylation catalysts. The zeolites employed in these prior artprocesses are zeolites X and Y. In addition, U.S. Pat. No. 5,053,571proposes the use of ruthenium and nickel supported on zeolite beta asthe aromatic hydroalkylation catalyst. However, these earlier proposalsfor the hydroalkylation of benzene suffer from the problems that theselectivity to cyclohexylbenzene is low, particularly at economicallyviable benzene conversion rates, and that large quantities of unwantedby-products, particularly cyclohexane and methylcyclopentane, areproduced.

More recently, U.S. Pat. No. 6,037,513 has disclosed thatcyclohexylbenzene selectivity in the hydroalkylation of benzene can beimproved by contacting the benzene and hydrogen with a bifunctionalcatalyst comprising at least one hydrogenation metal and a molecularsieve of the MCM-22 family. The hydrogenation metal is preferablyselected from palladium, ruthenium, nickel, cobalt and mixtures thereofand the contacting step is conducted at a temperature of about 50 to350° C., a pressure of about 100 to 7000 kPa, a benzene to hydrogenmolar ratio of about 0.01 to 100 and a WHSV of about 0.01 to 100. The'513 patent discloses that the resultant cyclohexylbenzene can then beoxidized to the corresponding hydroperoxide and the peroxide decomposedto the desired phenol and cyclohexanone.

According to the present invention, it has now been found that when abifunctional catalyst comprising an aluminosilicate molecular sieve ofthe MCM-22 family and a hydrogenation metal is used to effecthydroalkylation of benzene, the catalyst exhibits enhanced selectivityto monocyclohexylbenzene and reduced selectivity to dicyclohexylbenzeneand cyclohexane, when the acid-to-metal molar ratio (defined as thenumber of moles of the aluminum in the molecular sieve to the number ofmoles of the hydrogenation metal) of the catalyst is from about 75 toabout 750.

SUMMARY

In one aspect, the invention resides in a process for producingcyclohexylbenzene, the process comprising:

(a) feeding benzene and hydrogen to at least one reaction zone;

(b) contacting the benzene and hydrogen in said at least one reactionzone under hydroalkylation conditions with a catalyst system comprisingan aluminosilicate molecular sieve having an X-ray diffraction patternincluding d-spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and3.42±0.07 Angstrom, and at least one hydrogenation metal to produce aneffluent containing cyclohexylbenzene, wherein the catalyst system hasan acid-to-metal molar ratio (defined as the number of moles of thealuminum in the molecular sieve to the number of moles of thehydrogenation metal) of from about 75 to about 750.

Conveniently, the catalyst system has an acid-to-metal molar ratio offrom about 100 to about 300.

Conveniently, the molecular sieve is selected from MCM-22, PSH-3,SSZ-25, ERB-1, ITQ-1, ITQ-2, MCM-36, MCM-49, MCM-56, UZM-8, and mixturesof any two or more thereof, and especially MCM-22, MCM-49, MCM-56 andisotypes thereof.

Conveniently, said at least one hydrogenation metal is selected frompalladium, ruthenium, nickel, zinc, tin, and cobalt, especiallypalladium.

In one embodiment, at least 50 wt %, more preferably at least 75 wt %,and most preferably substantially all (even 100 wt %), of said at leastone hydrogenation metal is supported on an inorganic oxide differentfrom said molecular sieve, such as an oxide of one of Groups 2, 4, 13and 14 of the Periodic Table of Elements. Such oxide preferablycomprises alumina and/or titania and/or zirconia.

Conveniently, the hydroalkylation conditions include a temperature inthe range of about 100 to 400° C. Conveniently, the hydroalkylationpressure is in the range of about 100 to 7000 kPaa.

In a further aspect, the invention resides in a method for coproducingphenol and cyclohexanone, the method comprising producingcyclohexylbenzene by the process described herein, oxidizing thecyclohexylbenzene to produce cyclohexylbenzene hydroperoxide andcleaving the cyclohexylbenzene hydroperoxide to produce phenol andcyclohexanone.

DETAILED DESCRIPTION

Described herein is a process for the hydroalkylation of benzene toproduce cyclohexylbenzene and then the conversion of thecyclohexylbenzene in a two step process to cyclohexanone and phenol.Insofar as the hydroalkylation step produces dicyclohexylbenzene inaddition to the desired monocyclohexylbenzene product, the process caninclude the further step of transalkylating the dicyclohexylbenzene withadditional benzene to produce additional monocyclohexylbenzene product.

Benzene Hydroalkylation

The first step in the present process comprises contacting benzene withhydrogen under hydroalkylation conditions in the presence of ahydroalkylation catalyst whereby the benzene undergoes the followingreaction to produce cyclohexylbenzene (CHB):

Competing reactions include the complete saturation of the benzene toproduce cyclohexane, dialkylation to produce dicyclohexylbenzene andreorganization alkylation reactions to produce impurities, such asmethylcyclopentylbenzene (MCPB). Although dicyclohexylbenzene can betransalkylated to produce additional CHB product, conversion tocyclohexane represents loss of valuable feed, whereas impurities such asmethylcyclopentylbenzene (MCPB) are particularly undesirable since theboiling point of MCPB is very close to that of CHB so that it is verydifficult to separate MCPB from CHB. It is therefore important tomaximize the selectivity to cyclohexylbenzenes in the hydroalkylationreaction.

Any commercially available benzene feed can be used in thehydroalkylation step, but preferably the benzene has a purity level ofat least 99 wt %. Similarly, although the source of hydrogen is notcritical, it is generally desirable that the hydrogen is at least 99 wt% pure.

Preferably, the total feed to the hydroalkylation step contains lessthan 1000 ppm, such as less than 500 ppm, for example less than 100 ppm,water. Preferably, the total feed typically contains less than 100 ppm,such as less than 30 ppm, for example less than 3 ppm, sulfur.Preferably, the total feed contains less than 10 ppm, such as less than1 ppm, for example less than 0.1 ppm, nitrogen. In a particularlypreferred embodiment at least two, and preferably all three of the abovementioned preferred levels for water, sulfur and nitrogen are achieved.

The hydroalkylation reaction can be conducted in a wide range of reactorconfigurations including fixed bed, slurry reactors, and/or catalyticdistillation towers. In addition, the hydroalkylation reaction can beconducted in a single reaction zone or in a plurality of reaction zones,in which at least the hydrogen is introduced to the reaction in stages.Generally, the ratio of the total number of moles of hydrogen fed to thereaction to the number of moles of benzene fed to the reaction isbetween about 0.15:1 to about 15:1, for example from about 0.3:1 toabout 1:1, such as between about 0.4:1 and about 0.9:1. Suitabletemperatures for conducting the hydroalkylation reaction are betweenabout 100° C. and about 400° C., such as between about 125° C. and about250° C. Suitable reaction pressures are between about 100 and about7,000 kPaa, such as between about 500 and about 5,000 kPaa.

The catalyst employed in the hydroalkylation reaction is a bifunctionalcatalyst comprising an aluminosilicate molecular sieve of the MCM-22family and a hydrogenation metal. The term “MCM-22 family material” (or“material of the MCM-22 family” or “molecular sieve of the MCM-22family”), as used herein, includes one or more of:

-   -   molecular sieves made from a common first degree crystalline        building block unit cell, which unit cell has the MWW framework        topology. (A unit cell is a spatial arrangement of atoms which        if tiled in three-dimensional space describes the crystal        structure. Such crystal structures are discussed in the “Atlas        of Zeolite Framework Types”, Fifth edition, 2001, the entire        content of which is incorporated as reference);    -   molecular sieves made from a common second degree building        block, being a 2-dimensional tiling of such MWW framework        topology unit cells, forming a monolayer of one unit cell        thickness, preferably one c-unit cell thickness;    -   molecular sieves made from common second degree building blocks,        being layers of one or more than one unit cell thickness,        wherein the layer of more than one unit cell thickness is made        from stacking, packing, or binding at least two monolayers of        one unit cell thickness. The stacking of such second degree        building blocks can be in a regular fashion, an irregular        fashion, a random fashion, or any combination thereof; and    -   molecular sieves made by any regular or random 2-dimensional or        3-dimensional combination of unit cells having the MWW framework        topology.

Molecular sieves of the MCM-22 family generally have an X-raydiffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15,3.57±0.07 and 3.42±0.07 Angstrom. The X-ray diffraction data used tocharacterize the material are obtained by standard techniques such asusing the K-alpha doublet of copper as the incident radiation and adiffractometer equipped with a scintillation counter and associatedcomputer as the collection system. Molecular sieves of MCM-22 familyinclude MCM-22 (described in U.S. Pat. No. 4,954,325), PSH-3 (describedin U.S. Pat. No. 4,439,409), SSZ-25 (described in U.S. Pat. No.4,826,667), ERB-1 (described in European Patent No. 0293032), ITQ-1(described in U.S. Pat. No. 6,077,498), ITQ-2 (described inInternational Patent Publication No. WO97/17290), MCM-36 (described inU.S. Pat. No. 5,250,277), MCM-49 (described in U.S. Pat. No. 5,236,575),MCM-56 (described in U.S. Pat. No. 5,362,697), UZM-8 (described in U.S.Pat. No. 6,756,030), and mixtures of any two or more thereof.Preferably, the molecular sieve is selected from (a) MCM-49, (b) MCM-56and (c) isotypes of MCM-49 and MCM-56, such as ITQ-2.

Any known hydrogenation metal can be employed in the presenthydroalkylation catalyst although suitable metals include palladium,ruthenium, nickel, zinc, tin, and cobalt, with palladium beingparticularly advantageous. In particular, the amount of hydrogenationmetal present in the catalyst is selected such that the molar ratio ofthe aluminum in the molecular sieve to the hydrogenation metal is fromabout 75 to about 750, such as from about 100 to about 300.

The hydrogenation metal may be directly supported on the (MCM-22 family)molecular sieve by, for example, impregnation or ion exchange. However,in a more preferred embodiment, at least 50 wt %, for example at least75 wt %, and generally substantially all of the hydrogenation metal issupported on an inorganic oxide separate from but composited with themolecular sieve. In particular, it is found that by supporting thehydrogenation metal on the inorganic oxide, the activity of the catalystand its selectivity to cyclohexylbenzene and dicyclohexylbenzene areincreased as compared with an equivalent catalyst in which thehydrogenation metal is supported on the molecular sieve.

The inorganic oxide employed in such a composite hydroalkylationcatalyst is not narrowly defined provided it is stable and inert underthe conditions of the hydroalkylation reaction. Suitable inorganicoxides include oxides of Groups 2, 4, 13 and 14 of the Periodic Table ofElements, such as alumina and/or titania and/or zirconia. As usedherein, the numbering scheme for the Periodic Table Groups is asdisclosed in Chemical and Engineering News, 63(5), 27 (1985). When thecatalyst system comprises a composite of the aluminosilicate molecularsieve and the inorganic oxide that is different from the molecularsieve, these two components are conveniently present in a weight ratioin the range 90:10 to 10:90, such as 80:20 to 20:80, for example 70:30to 30:70 or 60:40 to 40:60.

In the above-mentioned preferred embodiment, the hydrogenation metal isdeposited on the inorganic oxide, conveniently by impregnation, beforethe metal-containing inorganic oxide is composited with the molecularsieve. Typically, the catalyst composite is produced byco-pelletization, in which a mixture of the molecular sieve and themetal-containing inorganic oxide are formed into pellets at highpressure (generally about 350 to about 350,000 kPa), or by co-extrusion,in which a slurry of the molecular sieve and the metal-containinginorganic oxide, optionally together with a separate binder, are forcedthrough a die. If necessary, additional hydrogenation metal cansubsequently be deposited on the resultant catalyst composite.

Suitable binder materials include synthetic or naturally occurringsubstances as well as inorganic materials such as clay, silica and/ormetal oxides. The latter may be either naturally occurring or in theform of gelatinous precipitates or gels including mixtures of silica andmetal oxides. Naturally occurring clays which can be used as a binderinclude those of the montmorillonite and kaolin families, which familiesinclude the subbentonites and the kaolins commonly known as Dixie,McNamee, Georgia and Florida clays or others in which the main mineralconstituent is halloysite, kaolinite, dickite, nacrite or anauxite. Suchclays can be used in the raw state as originally mined or initiallysubjected to calcination, acid treatment or chemical modification.Suitable metal oxide binders include silica, alumina, zirconia, titania,silica-alumina, silica-magnesia, silica-zirconia, silica-thoria,silica-beryllia, silica-titania as well as ternary compositions such assilica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesiaand silica-magnesia-zirconia.

Although the hydroalkylation step is highly selective towardscyclohexylbenzene, the effluent from the hydroalkylation reaction willnormally contain some dialkylated products, as well as unreactedaromatic feed and the desired monoalkylated species. The unreactedaromatic feed is normally recovered by distillation and recycled to thealkylation reactor. The bottoms from the benzene distillation arefurther distilled to separate the monocyclohexylbenzene product from anydicyclohexylbenzene and other heavies. Depending on the amount ofdicyclohexylbenzene present in the reaction effluent, it may bedesirable to transalkylate the dicyclohexylbenzene with additionalbenzene to maximize the production of the desired monoalkylated species.

Transalkylation with additional benzene is typically effected in atransalkylation reactor, separate from the hydroalkylation reactor, overa suitable transalkylation catalyst, such as a molecular sieve of theMCM-22 family, zeolite beta, MCM-68 (see U.S. Pat. No. 6,014,018),zeolite Y or mordenite. The transalkylation reaction is typicallyconducted under at least partial liquid phase conditions, which suitablyinclude a temperature of about 100 to about 300° C. and/or a pressure ofabout 800 to about 3500 kPa and/or a weight hourly space velocity ofabout 1 to about 10 hr⁻¹ on total feed and/or abenzene/dicyclohexylbenzene weight ratio about of 1:1 to about 5:1.

Cyclohexylbenzene Oxidation

In order to convert the cyclohexylbenzene into phenol and cyclohexanone,the cyclohexylbenzene is initially oxidized to the correspondinghydroperoxide. This is accomplished by introducing an oxygen-containinggas, such as air, into a liquid phase containing the cyclohexylbenzene.Unlike cumene, atmospheric air oxidation of cyclohexylbenzene in theabsence of a catalyst is very slow and hence the oxidation is normallyconducted in the presence of a catalyst.

Suitable catalysts for the cyclohexylbenzene oxidation step are theN-hydroxy substituted cyclic imides described in U.S. Pat. No. 6,720,462and incorporated herein by reference, such as N-hydroxyphthalimide,4-amino-N-hydroxyphthalimide, 3-amino-N-hydroxyphthalimide,tetrabromo-N-hydroxyphthalimide, tetrachloro-N-hydroxyphthalimide,N-hydroxyhetimide, N-hydroxyhimimide, N-hydroxytrimellitimide,N-hydroxybenzene-1,2,4-tricarboximide, N,N′-dihydroxy(pyromelliticdiimide), N,N′-dihydroxy(benzophenone-3,3′,4,4′-tetracarboxylicdiimide), N-hydroxymaleimide, pyridine-2,3-dicarboximide,N-hydroxysuccinimide, N-hydroxy(tartaric imide),N-hydroxy-5-norbornene-2,3-dicarboximide,exo-N-hydroxy-7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide,N-hydroxy-cis-cyclohexane-1,2-dicarboximide,N-hydroxy-cis-4-cyclohexene-1,2dicarboximide, N-hydroxynaphthalimidesodium salt or N-hydroxy-o-benzenedisulphonimide. Preferably, thecatalyst is N-hydroxyphthalimide. Another suitable catalyst isN,N′,N″-trihydroxyisocyanuric acid.

These materials can be used either alone or in the presence of a freeradical initiator and can be used as liquid-phase, homogeneous catalystsor can be supported on a solid carrier to provide a heterogeneouscatalyst. Typically, the N-hydroxy substituted cyclic imide or theN,N′,N″-trihydroxyisocyanuric acid is employed in an amount between0.0001 mol % to 15 wt %, such as between 0.001 to 5 wt %, of thecyclohexylbenzene.

Suitable conditions for the oxidation step include a temperature betweenabout 70° C. and about 200° C., such as about 90° C. to about 130° C.and/or a pressure of about 50 to 10,000 kPa. Any oxygen-containing gas,preferably air, can be used as the oxidizing medium. The reaction cantake place in batch reactors or continuous flow reactors. A basicbuffering agent may be added to react with acidic by-products that mayform during the oxidation. In addition, an aqueous phase may beintroduced, which can help dissolve basic compounds, such as sodiumcarbonate.

Hydroperoxide Cleavage

The final reactive step in the conversion of the cyclohexylbenzene intophenol and cyclohexanone involves cleavage of the cyclohexylbenzenehydroperoxide, which is conveniently effected by contacting thehydroperoxide with a catalyst in the liquid phase. This is convenientlycarried out at a temperature of about 20° C. to about 150° C., such asabout 40° C. to about 120° C. and/or a pressure of about 50 to about2,500 kPa, such as about 100 to about 1000 kPa. The cyclohexylbenzenehydroperoxide is preferably diluted in an organic solvent inert to thecleavage reaction, such as methyl ethyl ketone, cyclohexanone, phenol orcyclohexylbenzene, to assist in heat removal. The cleavage reaction isconveniently conducted in a catalytic distillation unit.

The catalyst employed in the cleavage step can be a homogeneous catalystor a heterogeneous catalyst.

Suitable homogeneous cleavage catalysts include sulfuric acid,perchloric acid, phosphoric acid, hydrochloric acid andp-toluenesulfonic acid. Ferric chloride, boron trifluoride, sulfurdioxide and sulfur trioxide are also effective homogeneous cleavagecatalysts. The preferred homogeneous cleavage catalyst is sulfuric acid,with preferred concentrations in the range of 0.05 to 0.5 wt %. For ahomogeneous acid catalyst, a neutralization step preferably follows thecleavage step. Such a neutralization step typically involves contactwith a basic component, with subsequent decanting of a salt-enrichedaqueous phase.

A suitable heterogeneous catalyst for use in the cleavage ofcyclohexylbenzene hydroperoxide includes a smectite clay, such as anacidic montmorillonite silica-alumina clay, as described in U.S. Pat.No. 4,870,217, the entire disclosure of which is incorporated herein byreference.

The crude cyclohexanone and crude phenol from the cleavage step may besubjected to further purification to produce purified cyclohexanone andphenol. A suitable purification process includes, but is not limited to,a series of distillation towers to separate the cyclohexanone and phenolfrom other species.

The following Example is given for illustrative purposes and does notlimit the scope of the invention.

Example 1

To illustrate the importance of acid/metal ratio in hydroalkylation overMCM-22 family molecular sieves, back-to-back experiments were conductedon two catalysts prepared identically except for the acid/metal ratio.Both of these catalysts contained 2 g of 0.3 wt % Pd supported on gammaalumina. The Pd/Al₂O₃ hydrogenation catalyst was then co-pelletized withHMCM-49 aluminosilicate molecular sieve (silica to alumina molar ratioof 18). The main difference between catalyst A and catalyst B (seeTable 1) was that the former contained 1.6 g MCM-49 catalyst whereas thelatter contained 4.8 g MCM-49. The molar ratio of the aluminum in MCM-49to Pd was 50 for catalyst A. The corresponding ratio for catalyst B was150.

Catalysts A and B were tested under nominally identical conditions. Thebenzene feed rate was 0.08 cc/min while the hydrogen feed rate was 10cc/min. The reaction temperature was 150° C. while the pressure was 1034kPag (150 psig). The results are summarized in Table 1.

TABLE 1 Catalyst A B Acid/metal molar ratio 50 150 Conversion, wt % 43.542.5 Selectivity, wt % Cyclohexane 7.1 3.2 Cyclohexylbenzene 70.8 78.0Dicyclohexylbenzene 17.3 13.8 Others 4.8 5.0

As can be seen from Table 1, the performance of catalyst B was superiorto the performance of catalyst A. The conversion of both catalysts wascomparable (42 versus 43 wt % conversion) but the total selectivitytowards cyclohexylbenzene and dicyclohexylbenzene was nearly 92 wt % forcatalyst B which was significantly higher than the selectivity of 88%for catalyst A. In addition, catalyst B was significantly more selectivetowards monocyclohexylbenzene than catalyst A (78 wt % versus 70.8 wt%).

While the present invention has been described and illustrated byreference to particular embodiments, those of ordinary skill in the artwill appreciate that the invention lends itself to variations notnecessarily illustrated herein. For this reason, then, reference shouldbe made solely to the appended claims for purposes of determining thetrue scope of the present invention.

1. A process for producing cyclohexylbenzene, the process comprising:(a) feeding benzene and hydrogen to at least one reaction zone; (b)contacting the benzene and hydrogen in said at least one reaction zoneunder hydroalkylation conditions with a catalyst system comprising analuminosilicate molecular sieve having an X-ray diffraction patternincluding d-spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and3.42±0.07 Angstrom, and at least one hydrogenation metal to produce aneffluent containing cyclohexylbenzene, wherein the catalyst system hasan acid-to-metal molar ratio of from 75 to
 750. 2. The process of claim1, wherein the catalyst system has an acid-to-metal molar ratio of from100 to
 300. 3. The process of claim 1, wherein the molecular sieve isselected from MCM-22, PSH-3, SSZ-25, ERB-1, ITQ-1, ITQ-2, MCM-36,MCM-49, MCM-56, UZM-8, and combinations of any two or more thereof. 4.The process of claim 3 wherein the molecular sieve is selected fromMCM-22, MCM-49, MCM-56 and combinations of any two or more thereof. 5.The process of claim 1, wherein the at least one hydrogenation metal isselected from palladium, ruthenium, nickel, zinc, tin, and cobalt. 6.The process of claim 5 wherein the hydrogenation metal comprisespalladium.
 7. The process of claim 1, wherein at least 50 wt % of thehydrogenation metal is supported on an inorganic oxide different fromthe molecular sieve.
 8. The process of claim 7 wherein at least 75 wt %of the hydrogenation metal is supported on the inorganic oxide.
 9. Theprocess of claim 8 wherein substantially all of the hydrogenation metalis supported on the inorganic oxide.
 10. The process of claim 7 whereinthe at least one hydrogenation metal is applied to the inorganic oxidebefore the inorganic oxide is composited with the molecular sieve. 11.The process of claim 7 wherein the inorganic oxide comprises an oxide ofat least one element of Groups 2, 4, 13 and 14 of the Periodic Table ofElements.
 12. The process of claim 11 wherein the inorganic oxidecomprises alumina and/or titania and/or zirconia.
 13. The process ofclaim 1, wherein the hydroalkylation conditions include a temperature of100 to 400° C. and/or a pressure of 100 to 7000 kPaa.
 14. The process ofclaim 1, wherein the ratio of the total number of moles of hydrogen fedto said contacting to the number of moles of benzene fed to saidcontacting is between 0.15:1 and 15:1.
 15. The process of claim 1,wherein the effluent also contains dicyclohexylbenzene and at least partof the dicyclohexylbenzene is contacted with benzene undertransalkylation conditions to produce further cyclohexylbenzene.
 16. Amethod for coproducing phenol and cyclohexanone, the method comprisingproducing cyclohexylbenzene by the process of claim 1, oxidizing thecyclohexylbenzene to produce cyclohexylbenzene hydroperoxide andcleaving the cyclohexylbenzene hydroperoxide to produce phenol andcyclohexanone.